1. Technical Field
The present invention pertains to the field of wireless communication, especially via telecommunication networks according to 3GPP specifications. More particularly, the present invention is related to processes performed in connection with uplinking packets by a user equipment device to a radio access network per high speed uplink packet access (HSUPA), and even more particularly, to hybrid automatic repeat request (HARQ) flushing by a user equipment device.
2. Discussion of Related Art
The present invention concerns flushing a buffer used by a user equipment (UE) device, i.e. a wireless terminal used by a user, for HARQ processes in connection with so-called high speed uplink packet access (HSUPA) used with the radio access network of UMTS (Universal Mobile Telecommunications System), i.e. the so-called UMTS terrestrial radio access network (UTRAN). A UE device includes a so-called mobile terminal component for communicating with a UTRAN. (A UE device could be a so-called mobile station or cellular telephone, but could also be for example a computer including the mobile terminal component.)
Per 3GPP (3rd Generation Partnership Program, a consortium of wireless telecommunication companies), any UTRAN includes typically several radio network controllers (RNCs), each controlling several so-called Node Bs—also known as base stations. A UE device, such as a mobile phone, is allowed to uplink up to, but not exceeding, a maximum allowable rate or power that is communicated to the UE device by the Node B serving the UE device (a.k.a. the serving Node B). The UE holds the data (packets) for uplink in a send buffer until the packets are successfully communicated to the Node B. Such a send buffer is therefore used in connection with HARQ processes in the Node B, in which the Node B combines two or more copies of the same packet, each copy possibly received in error, in order to correctly determine the packet that was actually sent. When a packet is successfully received by the Node B, i.e. when the Node B correctly determines the packet that was sent, possibly by combining copies, the UE removes the packet from its send buffer.
In case of HSUPA, the UTRAN (and in particular, e.g. the serving RNC, or possibly a Node B in communication with the UE) may from time to time determine that the UE send buffer should be flushed (i.e. that all packets should be removed) even though some packets have not been indicated as successfully received. (Usually, the UE determines that a packet has been successfully received because of not receiving a repeat request within a set period of time.)
Such HSUPA HARQ process flushing is required for example when performing reconfiguration, as part of the overall process of reconfiguration. A reconfiguration procedure can include reconfiguration of several different aspects of a communication link. For example, a reconfiguration procedure can include Data Description Indicator (DDI) reconfiguration. The DDI is a MAC-e (media access control-e) header field used to identify the logical channel, the MAC-d flow, and also the size of the MAC-d PDUs (protocol data units) concatenated into a MAC-es PDU. See e.g. the third generation partnership program (3GPP) technical specification (TS) 25.321 for a specification of DDI.
DDI reconfiguration re-maps the MAC-d flows, i.e. it reorganizes how data is to be mapped to the physical channels. The send buffer is maintained by the physical layer, i.e. the packets in the send buffer have already been passed to the physical layer. If reconfiguration including DDI reconfiguration is performed before HARQ process flushing, and there are still packets in the send buffer of the UE device, the re-mapping could interfere with transmission of these packets. On the other hand, if the reconfiguration does not involve re-mapping of MAC-d flows, etc., then it may be more advantageous to keep the retransmissions, i.e. not perform HARQ process flushing.
There is currently no method by which the UTRAN can signal to a UE to perform HSUPA HARQ process flushing.
What is needed therefore is a way for the UTRAN to indicate to the UE when to flush its send buffer, i.e. when to perform HSUPA HARQ process flushing.